XML 79 R59.htm IDEA: XBRL DOCUMENT v3.20.4
Revenue (Narratives) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Revenue from Contract with Customer [Abstract]      
Revenue recognition previously deferred $ 764 $ 762 $ 740
Remaining revenue recognition $ 22,000    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01      
Revenue from Contract with Customer [Abstract]      
Remaining performance obligation, percentage 32.00%    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]      
Performance obligations expected to be satisfied, expected timing 12 months    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01      
Revenue from Contract with Customer [Abstract]      
Remaining performance obligation, percentage 22.00%    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]      
Performance obligations expected to be satisfied, expected timing 24 months